20=3.14*x^2*4

Solution for 20=3.14*x^2*4 equation:

Simplifying
20 = 3.14x2 * 4

Reorder the terms for easier multiplication:
20 = 3.14 * 4x2

Multiply 3.14 * 4
20 = 12.56x2

Solving
20 = 12.56x2

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add '-12.56x2' to each side of the equation.
20 + -12.56x2 = 12.56x2 + -12.56x2

Combine like terms: 12.56x2 + -12.56x2 = 0.00
20 + -12.56x2 = 0.00

Add '-20' to each side of the equation.
20 + -20 + -12.56x2 = 0.00 + -20

Combine like terms: 20 + -20 = 0
0 + -12.56x2 = 0.00 + -20
-12.56x2 = 0.00 + -20

Combine like terms: 0.00 + -20 = -20
-12.56x2 = -20

Divide each side by '-12.56'.
x2 = 1.592356688

Simplifying
x2 = 1.592356688

Take the square root of each side:
x = {-1.261886163, 1.261886163}